1. Field of the Invention
The present invention relates generally to a steering apparatus for vehicles of the four-wheeled type. More particularly, the invention relates to a steering apparatus for turning rear wheels as well as front wheels of a vehicle by rotational movement of a steering wheel.
2. Description of Relevant Art
Four-wheeled vehicles are generally steered by turning front wheels with respect to the longitudinal axis of the vehicles. As the front wheels begin to be turned while the vehicle is running, an angle of slippage is developed at the front wheels, thereby producing a cornering force which causes the vehicle body to move transversely and to yaw about the center of gravity of the vehicle body.
An angle of slippage is generated at the rear wheels only after the vehicle body has started being displaced due to the yawing movement thereof. Therefore, a cornering force acts on the rear wheels a short interval of time after the cornering force has acted on the front wheels. In other words, there is a short time lag before a resultant combined cornering force on the front and rear wheels reaches a value the driver is expecting, resulting in one of the difficulties associated with driving a four-wheeled vehicle.
While the four-wheeled vehicle is steered to move around, the wheels are subjected to lateral slippage, such that the longitudinal axis or orientation of the vehicle tends to be out of alignment with a tangential line on an arcuate path upon which the vehicle moves, resulting in another difficulty associated with driving a four-wheeled vehicle.
In view of the foregoing difficulties, the driver of a four-wheeled vehicle must take into consideration a time lag between the turnings of the front and rear wheels, and an angular difference between the tangential line on the arc which the vehicle is to sweep, and the longitudinal axis of the vehicle. For proper and safe driving of four-wheeled vehicles, the driver must have considerable driving experience, because many traffic accidents result from movements of the vehicle which the driver does not fully expect at the time of steering operation.
The present invention overcomes the above described problems attendant conventional four-wheeled vehicles, and provides a steering apparatus wherein the rear wheels of the vehicle are also dirigible at the same time as the turning of the front wheels, and whereby the steering responsiveness is substantially improved.